Adaptive flow control scheme for real-time traffic in ATM networks

In communication networks with large delay-bandwidth product, congestion could happen over shorter time scales than those at which end-to-end protocols such as congestion control schemes typically operate. lin such cases, the congestion can dissipate rapidly before congestion feedback information returns to the source. Network designers therefore face a challenge. The bursty and cyclic nature of Variable Bit Rate (VER) traffic creates another issue for transmission in ATM networks. To reach the dual goals of keeping cell loss rate low and network utilization high, we propose an adaptive rate-based flow control scheme for real-time VER traffic in ATM networks. The goal of the scheme is to minimize the impact of traffic overload in order to limit the cell loss rate to an acceptable range and also increase the network utilization. The proposed flow control scheme is based on predicting the evolution of buffer occupancy over time using a Proportional-plus-Integral-plus-Derivative (PID) controller and a linear predictor to adaptively update the optimum data emission rate at the transmitter. The adaptive policy attempts to keep the buffer occupancy for each virtual channel at a steady level and the simulation results show that the proposed scheme works effectively against network congestion. Along with the design of the new flow control scheme, we also develop a hierarchically structured testbed to measure network performance and explore various flow control schemes in ATM networks with diverse classes of incoming traffic.